Research Review of the Key Technology and Application of Large-scale Water Electrolysis Powered by Renewable Energy to Hydrogen and Ammonia Production

The rapid development of new energy has brought opportunities and challenges to the electric power and chemical industry. On the one hand, the consumption of renewable energy leads to a large amount of waste of energy such as water and light. On the other hand, replacing carbon-based fossil energy ammonia with green hydrogen as raw material can greatly reduce the carbon emissions of the chemical industry. Therefore, the use of hydropower, photovoltaics, and other renewable energy sources to electrolyze water to produce hydrogen can provide green raw materials for ammonia synthesis, which can significantly improve the capacity of renewable energy consumption, reduce energy consumption, and carbon emissions, and serve the national goal of “carbon peaking and carbon neutrality”. However, the fluctuation of renewable energy power is difficult to meet the stability requirements of the traditional synthetic ammonia production process, and there are still many challenges in the design and operation of large-scale renewable energy electrolysis of water to produce hydrogen and synthetic ammonia. There is an urgent need to carry out systematic research and breakthroughs in key technologies for the integration and regulation of large-scale electrolysis of water for hydrogen production to ammonia synthesis systems that adapt to the fluctuating characteristics of renewable energy. In this regard, the process and its topology structure of the renewable energy electrolysis water and the synthesis ammonia process are firstly introduced, including the electrolysis water hydrogen production section, the compression buffer section, and the chemical ammonia synthesis section. Furthermore, the key technical system for the construction of the system was proposed, including the synthetic ammonia process multi-stable optimization and flexible control technology under the fluctuating conditions of renewable energy, the modular integration and cluster dynamic control technology for large-scale hydrogen production system by electrolytic water with “electricity–heat–mass” coupling, “source—grid—hydrogen—ammonia” system-wide coordinated control technology for the volatility of renewable energy and multi-stable characteristics of the chemical industry, comprehensive security protection and market operation for electricity, hydrogen, ammonia, and other elements mechanism. Contents include: Aiming at the optimization of the synthetic ammonia process and multi-stage cooperative regulation technology suitable for flexible production, a high-fidelity proxy model for synthetic ammonia is developed by integrating the subsystems of the synthetic tower, compressor, gas separation, and heat transfer network, considering the hydrogen storage and supply quantity and the performance of the catalyst. The adaptation scheme and collaborative control technology of each subsystem of water electrolysis for hydrogen production and ammonia synthesis under the fluctuation of renewable energy supply and market demand are studied. Aiming at the modular integration and cluster dynamic control technology of large-scale water electrolysis and hydrogen production system, the multi-time-scale time-domain simulation method of the cluster system is studied based on singular perturbation and surrogate model technology, and the multi-physical coupling state space model of the electrolytic cluster system is established. Considering the module startup-shutdown unit commitment scheduling, scheduling and power allocation between the modules, and safe operation of the interval constraint and electro-thermal interface features, to improve the hydrogen yield, improve energy efficiency, improve the power tracking and grid load frequency control as the goal, to build the multi-objective hierarchical cluster system scheduling and control model. Aiming at the whole system cooperative control technology of hydrogen energy participating in the power grid, the flexible operation method of multiple sections with steady-state operation characteristics of hydro-solar complementary power generation, power-to-hydrogen production, hydrogen storage, ammonia synthesis, and ammonia storage is studied, and the flexible dynamic cooperative control method of electric hydrogen production and ammonia synthesis system is also studied. The simulation model of electric hydrogen production and ammonia synthesis system with static equivalent and parameter aggregation methods is integrated. The optimal control method and technical index of the system with hydrogen and ammonia in the source grid are studied. Combined with the characteristics of frequency modulation and peak regulation, the strategy of power-to-hydrogen production and ammonia synthesis system participating in power system auxiliary service is studied. It has significant social benefits and strategic significance to improve the local consumption rate of renewable energy and the friendliness of grid-connected scheduling and reduce chemical carbon emissions and reduce chemical carbon emissions by building a large-scale water electrolysis system for hydrogen production and ammonia synthesis with renewable energy. © 2022 Editorial Department of Journal of Sichuan University. All rights reserved.